As solar rooftop systems continue appearing in homes and businesses nationwide, A new issue is being posed: combining more distributed solar generation so that more customers can efficiently reap the benefits of this renewable, clean energy source. There is no place where this growth and the challenge are more evident than in Hawaii’s utility companies such as the Hawaiian Electric Companies – where solar power systems supply approximately 20 times more energy into the electrical grid than is typical across the entire mainland United States.
Typically, rooftop photovoltaic and PV systems are connected to medium voltage distribution grids related to high voltage transmission lines and have a one-way power flow. With the large amount of solar distributed, utility companies such as Hawaiian Electric are becoming concerned that solar power could exceed electricity demand, resulting in reverse power flow and over-voltage, which could lead to disruptions to service. In Hawaii, around 2700 homes that could be powered by solar are located on grids with solar energy that exceeds the daily minimum load. As a result, these homes aren’t in a position to connect solar panels to the grid.
To gain a greater understanding of the ways solar power systems work with distribution systems for utilities and allow more homes powered by solar power to be connected to the grid without risk and securely, the Energy Department’s National Renewable Energy Laboratory (NREL) and SolarCity the nation’s largest solar power company – have recently teamed up along with Hawaiian Electric to analyze high-penetration solar scenarios and tackle operational concerns using sophisticated computer models.
In particular, Hawaiian Electric and SolarCity are evaluating advanced inverters that convert the direct-current energy generated by solar panels to alternating current used by the power grid – in the Energy Systems Integration Facility at NREL in Golden, Colo. Advanced inverters come with features that aid the power grid in responding to grid disturbances like t, the power plant shutdown or a significant load that goes off.
Recent tests have looked at scenarios where large loads go off, which causes the grid to increase its operating voltage temporarily. The results allowed Hawaiian Electric to approve solar power systems for customers who want connections to lines with sizeable solar power penetrations.
New customers will require sophisticated inverters, but their impact is enormous because it will allow more than 2,500 clients to link their solar energy devices to the Hawaiian Electric grid by next April.
This collaboration and a prior partnership with Hawaiian Electric and SolarCity with the University of Hawaii to demonstrate innovative inverters in the field were funded through the Department of Energy’s SunShot Initiative. In line with the SunShot mission, this project is aiding utilities and researchers to comprehend how to utilize solar technology in a secure, reliable, cost-effective, and efficient method.